A Mach-Zehnder interferometer (MZI) for high temperature (1 000℃) sensing based on few mode fiber (FMF) was proposed and experimentally demonstrated. The sensor was fabricated by fusing a section of FMF between two single-mode fibers (SMFs). The structure was proven to be an excellent high temperature sensor with good stability, repeatability, and high temperature sensitivity (48.2 pm/℃) after annealing process at a high temperature lasting some hours, and a wide working temperature range (from room temperature to 1 000℃). In addition, the simple fabrication process and the low cost offered a great potential for sensing in high temperature environments.